<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var score = prompt('请输入分数：')
        if(score>=90) {
            alert('等级为:A');
        }else if(score>=80  ) {
            alert('等级为:B');
        }else if(score>=70  ) {
            alert('等级为:C');
        }else if(score>=60  ) {
            alert('等级为:D');
        }else {
            alert('等级为:E');
        }
    </script>
</head>
<body>
    
</body>
</html>